1. Field of the Invention
The present invention relates to a system for recording digital data for maintenance, namely prevention of tampering or changing of digital data transferred via memory for temporarily storing data from a digital data input device such as a digital camera, particularly to a system capable of preventing changes to a digital photograph for assessment of non-life insurance or for recording work on a building site taken by a digital camera.
2. Description of the Related Art
In recent years, digital data is increasingly used in a number of fields due to rapid proliferation of consumer digital devices such as a digital camera. However, digital data is accompanied by a risk to be used as evidence since there is a danger of contents being changed without leaving a trace. In order for a recipient of data to trust any data, there should be a means for assuring that the data has not been changed since it was acquired.
As a method to prevent tampering or changing of digital data, there are methods such as MAC (Message Authentication Coding) where an electronic signature created by a one-way hash function is transferred being attached to the data. In the case of a digital image, it is also possible to further enhance conformity of the electronic signature with an embedded image by using an electronic watermark in the image (for instance, Japanese Unexamined Patent Publication No. Hei 10-164549).
However, if application to a digital photograph which supposedly needs this technology most of all is considered, it will be inside a camera that an electronic signature is implemented. In that case, a more reliable system is desired since an encryption key stored in the camera is fixed in addition to high load of computation on the camera. Namely, a method which is implementable within constraints of current hardware and capable of ensuring necessary and sufficient integrity of data has been required.
An object of the present invention is to resolve the above-mentioned problem and to provide a system for authenticating digital data capable of preventing change or disguise of data by improvement or interchange in case of no confidentiality in the data itself so as to maintain the data.